Halifax and Bank of Scotland have become the latest credit card providers to quietly push through big increases in interest rates charged to customers.

HBOS, the parent group to both providers, and now owned by Lloyds Banking Group, says the majority of rises are between 1% and 4%. But some Halifax card users are receiving letters this week which increase their rate from 13.9% to 18.95% – a rise of 5%. A Bank of Scotland customer who contacted Guardian Money said her standard rate had jumped to 20.95%, with cash advances increased to 26.95%.

The rise in interest rates comes despite the fact that the Bank of England has slashed base rate to just 0.5%.

HBOS, now majority owned by the taxpayer, says it made the changes as part of a "continual review of rates". "The changes will affect a small number of our card holders and will be according to each customer's personal circumstances. The average increase is between 1% and 4% which is inside [government] guidelines and reflects what is happening across the credit card market," a spokeswoman for HBOS said.

Nationwide last month said it was upping the interest it charges across its card range. Anyone with a Nationwide Gold card will see their purchase rate increase from 15.9% annually to 16.9%, while the Classic card rate will increase from 17.9% to 19.9%. Both changes come into force on 6 May.

Last year MBNA raised the rate on several of the cards it supplies on behalf of UK banks from starting levels of 15.9% to 19.9% – and in some cases as high as 34.9%.

The latest move means anyone who uses a credit card but fails to pay off the balance at the end of each month needs to take a close look at their credit card statement to see how much they are now paying.